The present invention is related to electronic turn signal cancellation apparatus, and more particularly to such apparatus adaptable for use in automatically cancelling vehicle turn signal indications.
Typically electromechanical devices are currently used to provide automatic turn signal cancellation in automobiles after completion of a turn. Such devices primarily sense the angular rotation of the steering wheel to determine when the turn signal should be cancelled. In such devices a right or left turn signal indication is actuated by a driver operated switch and the turn signal indication is cancelled (reset) in response to a mechanical sensor device sensing a predetermined angular rotation of the vehicle steering wheel and then mechanically resetting the driver actuated switch. Typically these electromechanical devices are complex and expensive and comprise many individual mechanical linkage elements. The linkage elements of these devices are subject to mechanical wear and therefore are subject to potential reliability problems. These devices implement the resetting of the turn signal indicator switch in a mechanical, rather than electrical, manner.
Some electronic turn signal cancellation devices have been proposed, but typically these electronic systems utilize a large number of sensors to electronically determine both the direction of steering wheel rotation and the angular rotational position of the steering wheel since both of these pieces of information are needed to properly implement turn signal cancellation. Since a large number of sensors are used in these systems, this increases the cost of such turn signal cancellation systems to the point that these systems have not been readily commercially utilized in the automobile industry. Also, since the sensors are typically positioned at widely different angular locations this complicates the installation of the sensors.
In addition to the above deficiencies of prior systems, typically turn signal cancellation is accomplished without any hysteresis, meaning that once a predetermined angular position has been achieved by turning the steering wheel in a predetermined direction, even a very small reverse rotation of the steering wheel may result in cancellation of the turn signal. Many times this is undesirable since the actual vehicle turn may not have been completed. While some prior systems have noted that hysteresis may be desirable, their implementation apparatus does not appear to be readily adaptable to the utilization of a minimum number of positions sensors such that these systems also are not cost effective.